bogus address

It’s trivial to set up accounts on the free services in which you can be anonymous – using entirely fake information – or in which you can impersonate someone else.

I’m not sure I’d expect much help from the provider – Yahoo, in your case. To be honest, even if they did bother to reply, they wouldn’t know who to believe. You and I know that you’re not, but how’s Yahoo to know that you’re not the impersonator, or just someone trying to hassle someone else?